These days, there’s an overwhelming number of products to prevent parasites in pets. How do I know which one to choose?
Parasites, including ticks, fleas, worms and more, can wreak havoc on your pet’s health, and create headaches and messes for you. I just adopted a 7-week-old Labrador puppy, and I still haven’t quite recovered from my nightmarish experience of cleaning putrid diarrhea and piles of worms out of a crate at 2 a.m. No one needs that. Here’s what you need to know to make the best choice for prevention.
What parasites are problematic for pets?
An enormous number of parasites can cause disease in pets. Ectoparasites — think ticks, fleas, mosquitoes, mites and lice — cause disease from outside the body. Endoparasites, including heartworms, roundworms, hookworms, tapeworms and coccidia, cause disease internally. The particular parasites your pet is most likely to encounter depend on the part of the world you live in, your pet’s age and its lifestyle. For example, heartworm infestations are more common in the southern United States, and intestinal worms are more common in puppies and kittens than adults. If your dog runs on trails, it’s more likely to be exposed to ticks.
It’s important to protect your pet because parasites can make them — and you or your family — sick.
Ectoparasites cause skin irritation, and some (such as ticks, fleas and lice) suck your pet’s blood, possibly leading to anemia and lethargy. Ectoparasites also carry pathogens that can cause life-threatening diseases, such as ehrlichiosis in dogs and cytauxzoonosis in cats. And they can transmit endoparasites — for example, heartworm disease from mosquitoes and tapeworms from fleas.
Some ectoparasites, such as scabies mites, also bite humans and cause itchy rashes. And the ticks and fleas that pets bring into the house can transmit infectious diseases to humans. That includes cat scratch disease, which is caused by a bacteria, Bartonella, which is transmitted by fleas. Cats (especially young cats) can have large quantities of bacteria in their blood without showing signs of illness. Fleas feeding on Bartonella–infected cats shed the bacteria in their poop (flea dirt or flea frass). The disease is called cat scratch disease because cats can force contaminated flea dirt into your skin when they scratch you. When Bartonella spreads to the body, most infected people develop lymph node enlargement near the site of the scratch, but in immunocompromised people, Bartonella can cause life-threatening heart, eye, spleen and liver disease.
Of the endoparasites, perhaps the most life-threatening are hookworms (which attach to the lining of your pet’s intestines and suck blood) and heartworms (which cause disease of the heart and pulmonary arteries). On top of being gross, roundworms and tapeworms are common causes of diarrhea, and they stunt growth in puppies and kittens.
Worms in your pet’s poop can also cause human disease. Hookworms can migrate through the skin, leading to a squiggly rash called cutaneous larva migrans (known for unsightly butt rashes in people who sit on dog-poop-contaminated beaches in the Caribbean). Kids who play in sandboxes contaminated with poop can inadvertently ingest roundworms, which can migrate to the eye and cause blindness (ocular larva migrans). Although rare in the United States, unwitting ingestion of eggs of the tapeworm Echinococcus can cause a life-threatening cystic liver disease.
Thankfully, all these diseases can be avoided by using appropriate pet parasite preventatives.
What’s the best way to prevent parasites?
Globally, pet parasite prevention products (known as parasiticides) are a multibillion-dollar market. Competition among animal pharmaceutical companies has driven the development of highly effective, safe and convenient products.
Choosing the right one for your pet can be complicated, so it’s best to talk to your vet about it. This is because:
Products are available in different formulations. These include topicals (also known as “spot-on” treatments), chewables, injectables and collars. Some products are long-acting (can be given monthly or every three months) and even ultralong-acting (can be given yearly).
Products differ in their ability to protect against parasites and diseases. There are preventatives that work against fleas but not ticks, as well as combination products designed to prevent fleas, ticks, heartworm and intestinal worms. Some products are labeled for prevention of American dog ticks (Dermacentor) but not lone star ticks (Amblyomma), or they need to be given more frequently to prevent Amblyomma ticks. Some products must be ingested by ticks and fleas to work, whereas others repel ticks and stop them from biting altogether. Many products now contain compounds known as isoxazolines (fluralaner, lotilaner, sarolaner, afoxolaner), which are very effective against fleas, ticks and mites, and work within eight hours. Products that repel ectoparasites are needed in regions where parasites can transmit pathogens within eight hours.
Current guidelines from the Companion Animal Parasite Council state that all dogs and cats should be treated year-round and throughout their lives for ticks, fleas, heartworm and intestinal parasites. However, evidence of parasiticide resistance has now been found in fleas, brown dog ticks, heartworms, hookworms and tapeworms, so a one-size-fits-all approach might not be the best way to go. The appearance of resistant parasites is a major concern that has led to the development of risk-based guidelines for use of pet parasiticides by groups such as the European Scientific Counsel Companion Animal Parasites and the Canadian Parasitology Expert Panel.
Are parasite preventatives safe?
Most products are very safe when used according to the label directions. However, many products that contain pyrethroids (including flea and tick products from pet stores) are poisonous for cats — so much so that using them even on a dog that lives with a cat can cause the cat to become ill.
There are also concerns about the environmental safety of pet parasiticides. Products that contain imidacloprid and fipronil are most concerning because these persist in the environment for long periods of time. In addition to being included in pet products, both have been widely used in agriculture to prevent crop damage. Because of imidacloprid’s negative effects on honeybees, its use on field crops has now been banned by the European Union. When pets treated with topical parasiticides or collars are bathed — or when they swim in lakes and rivers — parasiticides can contaminate the environment and cause toxicity in aquatic insects and fish. Researchers have also raised concerns about the effects on the reproduction of birds that incorporate contaminated pet fur into their nests.
The relative contribution of pet parasiticide use to environmental contamination versus agricultural use is still a topic of heated debate, but if your pet swims, it’s probably best to avoid using topical products known to be toxic to aquatic animals.
General tips on using parasiticides safely and responsibly:
- Use products only for the animal they’re prescribed for. Never use a dog product on a cat. Unless your vet says it’s safe, avoid using pyrethroid-containing products on dogs if you have cats in the house.
- Read and follow the product label directions carefully.
- Discuss treatment options with your vet to minimize environmental risks, including the best product if your pet swims or is bathed frequently.
- Return unused parasiticides to your vet for proper disposal.
- Pair the parasiticides with efforts to reduce parasites in the environment. Clear brush and long grass (ticks), reduce standing water (mosquitos), and pick up your pet’s poop and prevent your dog from eating poop (worms).
Have questions about your pet’s behavior, health or other issues? Use this form to submit them to Dr. Sykes.
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